While Chiyo and Rebecca definitely qualify, and maybe Konata (at 16, she's not really a little girl anymore), Mika is in her 20s.
Ruling: Mika is definitely cute, but she may not participate in the contest. Sorry.
Here's a picture of Ricotta from Dog Days
to cheer you up. http://www.crunchyroll.com/showphoto?id=4309732467